Paving machines are used to deposit layers of asphalt onto a roadway or parking lot bed. A paving machine generally includes a hopper that receives heated asphalt, a screed, and a conveying system that moves the heated asphalt from the hopper onto the bed in front of the screed. During operation, the screed is pushed or pulled over the asphalt to level and shape the asphalt into a layer of paving material having a desired thickness and width. The screed is typically connected to the paving machine via a hinged connection and is allowed to “float” on top of the asphalt and use its weight to level and shape the layer. In some applications, the paving machine is connected to and towed by a dump truck supplying the asphalt to the hopper. In other applications, the paving machine includes a tractor that self-powers the paving machine.
The thickness of the asphalt layer deposited by the paving machine is a function of multiple factors, including the speed of the paving machine, the feed rate of asphalt from the hopper, and the elevation of the point at which the screed is connected to the paving machine. During a paving operation, it can be difficult to determine whether the proper amount of asphalt is being applied to the bed and whether any of these factors should be adjusted until at least a significant portion of the bed has been covered with asphalt. As a result, portions of the bed may receive too much asphalt and incur a greater cost than anticipated, or receive too little asphalt and incur a penalty for failing to meet the customer's specifications. Similar situations may arise throughout the paving operation as the thickness and width of the layer is varied by the paving crew in accordance with the customer's specifications.
One attempt to monitor the amount of material deposited by a paving machine is disclosed in U.S. Pat. No. 8,930,092 B2 of Minich that issued on Jan. 6, 2015 (“the '092 patent”). Specifically, the '092 patent discloses an asphalt paver having a hopper for storing asphalt, a tractor drive system for transporting the hopper, and a variable-width screed attached to the tractor drive system. A conveyor transports asphalt from the hopper to the front of the screed via a tunnel, where an auger disperses the asphalt along the width of the screed. The width of the screed is sensed by width sensors attached to left and right sides of the screed. Material height sensors disposed within the tunnel measure the height of the material as it travels from the hopper to the screed, and motion detection devices measure the linear speed of the conveyor. Using a calibration curve, a computer system determines an incremental weight of asphalt being laid down by the paver based on the screed width, material height, and conveyor speed. Using the paver speed (as determined by a speed sensor), the computer system determines an instantaneous amount of paving material or “yield” being applied during the paving process as well as a total yield over period of paving time. The total yield is compared to an actual or “ticket” amount of asphalt delivered by a truck to determine whether all of the delivered asphalt was consumed by the paver.
Although the paver of the '092 patent may allow paver yield to me monitored, it may not be optimum. In particular, the paver of the '092 patent may not accurately determine how much asphalt has actually been applied since the height sensors used to determine the instantaneous yield may only reflect an amount of material on the conveyor, whereas the actual yield deposited may vary as paver and screed settings are adjusted during the paving process. Further, the calibration curve used to determine the weight of material may not be applicable to various types of paving materials having different properties, which may lead to inaccurate weight determinations.
The disclosed production monitoring system are directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.